Effects of mechanical control of aquatic vegetation on biomass, regrowth rates, and juvenile fish populations at saratoga lake, new york

Abstract

Experimental mechanical barge/conveyor harvesting conducted in June and August of 1981 and 1982 significantly reduced total plant biomass initially, relative to control areas. Regrowth of the predominant species, Eurasian watermilfoil (Myriophyllum spicatum), reached pre-harvest levels within 30 days after June and August harvestings. Total plant and M. spicatum biomass (g·m−2, dry) in harvested areas peaked later than control area vegetation both years, and was slightly higher. The ratio of the average annual biomass of the harvested area to the control area was the same both years (0.73), despite significant decreases in overall average total biomass in 1982. Similar harvesting resulted in the removal of primarily juvenile fish. Harvesting was conducted in dense littoral zone stands of milfoil (M. spicatum) and curly-leaf pondweed (Potamogeton crispus). The harvesting operation removed primarily bluegill sunfish (Lepomis macrochirus) and to a lesser degree, largemouth bass (Micropterus salmoides), yellow perch (Perca flavescens) and pumpkinseed sunfish (Lepomis gibbosus). Harvesting effectively removed approximately 2–3 percent of the total standing crop of juvenile fish in both June 1981 and 1982, and approximately 2–8 percent in August of both years. © 1984 Taylor & Francis Group, LLC.